An optical fiber sensor is a sensor that converts a state of an object to be measured into a measurable optical signal, and can be applied in monitoring fields of liquid level, pressure, deformation, temperature, flow velocity, and the like. An optical fiber flow sensor is more widely applied to engineering fields of seas, oilfields, and the like due to its advantages of high sensitivity, anti-electromagnetic interference, being easy for wavelength division multiplexing, and the like.
An optical fiber flow sensor monitors a flow velocity via a fiber detection element by a corresponding metal structure. In an optical fiber flow sensor, the fiber detection element needs to be sensitized and packaged, and usually is attached at a surface of a substrate material, such as a metal beam, by means of glue.
When the fiber detection element is attached on the metal beam, there would be a relatively large difference between expansion coefficients of the fiber detection element and the metal beam. In this case, a thermal mismatch phenomenon would arise under influence of temperature; and under influence of a high temperature, the glue becomes extremely unstable and a creep deformation would occur, thus resulting in an inaccurate final measurement result, and even a problem that the optical fiber flow sensor fails. In addition, use of an optical fiber flow sensor would lead to a contact-type measurement, in such a case, the fiber detection element, serving as a core measurement element, easily suffers from a hydrogen loss and corrosion. Therefore, an optical fiber flow sensor cannot be used for a long-run monitoring in severe environments such as an oil well and seawater.